High pressure mercury titanium iodine discharge lamp with phosphor coating

ABSTRACT

A high-efficiency, high-intensity blue-emitting discharge lamp combination in which, to the normal arc tube containing a predetermined amount of mercury and the normal outer envelope, there is added a phosphor coating of strontium chloro-apatite activated by divalent europium onto the interior surface of the outer envelope and there is also added titanium and iodine as discharge sustaining additives in the arc tubes. This combination provides a substantially more efficient high-intensity source of blue light than previous sources and is especially useful in the medical and photocopying fields.

United States Patent 1191 Larson June 28, 1974 [541 HIGH PRESSURE MERCURY-TITANIUM 3,670,194 6/1972 Thornton, Jr. et a1. 313/109 ggg g g ggfgg WITH FOREIGN PATENTS OR APPLICATIONS 902,160 6/1972 Canada [75] Inventor: Daniel A. Larson, Cedar Grove, NJ. 1 r [73] I Assignee: Westinghouse Electric Corporation, Primary Examiner-Palmer C. Demeo 1 Pittsbrugh, Pa. Attorney, Agent, or Firm-R. A. Stoltz [22] .Filed: Apr. 2, 1973 [211 Appl. 190.; 347,081 [57] M 5 A high-efficiency, high-intensity blue-emitting discharge lamp combination in which, to the normal arc v U-S- tube nt i i g a predetermined amount of mercury [5H t 4 61 B E 61/42 and the normal outer envelope, there is added aphos- 58 d Eng/109 i 229 phor coating of strontium chloro-apatite activated by I 1 are 1223/39; divalent europium onto the interior surface of the outer envelope and there is also added titanium and 56 1, R f d iodine as discharge sustaining additives in the are l e 1 e ereinces I e tubes. This combination provides a substantially more H STATES PATENTS efficient high-intensity source of blue light than previ- 2,748,303 5/1956 Thorington 313/25 ous sources and is especially useful in the medical and 3,279,877 10/1966 Smith et al..... 316/16 photocopying fi ld 3,599,028 8/l9 7l Wanmaker et 313/109 3,658,068 4/1972 McNall 128/395 1 2 Claims, 1 Drawing Figure v .1 HIGH PRESSURE MERCURY-TITANIUM IODINE "DISCHARGE LAMP WITH PHOSPHOR COATING CROSS-REFERENCE TO RELATED APPLICATIONS In copending application Ser. No. 347,082, filed Apr.

- 2, I973, by the present inventor and owned by the presentassignee, is disclosed a discharge lamp combination using a chromium iodide additive in addition to the mercury, and also using a phosphor coating of strontium chloro-apatite activated by divalent europium. A highly efficient high-intensity source of blue light is produced.

BACKGROUND OF THE INVENTION Thisinvention relates to high-pressure mercury discharge lamps for uses in which a large amount of blue emission is desired. Such uses include both photocopying and medical applications. v

Illustrative of the use of a blue-emitting lamp in the medical" field is U..S. Pat. No. 3,658,068 issued to McNall on Apr. 25, 1972 which discloses a lowpressure mercury (fluorescent) lamp having an alkaline-earth metal halophosphate (chloro-apatite) phosphor activated by divalent europium. This lamp is used optimum spectral distribution for such treatment has not been definitely determined, it is believed thatthe -.Z-bar spectral tristimulus value (see pages -4 and 55 of the-IES Lighting Handbook, 5th edition, 1972 i for the Z-bar spectral tristimulus value and normalizing to such a value) isa good measure of the desired specphosphor is strontium chloro-apatite activated by divalent europium. Typically such a lamp has a 'bluenormalized output per watt of about 100.

High-pressure mercury vapor discharge lamps using titanium iodide additives are also known in the art. Such a lamp for the generation of white light is described in Canadian Patent No. 902,160. Typically, such a lamp has a bluemormalized outputper watt of about US.

In the'fabrication of iodide additive lamps, tin iodide has been obtained, for example, by adding metallic tin and mercury iodide (from which tin iodide is formed during lamp operation). This is a more convenient method of iodine addition than adding tin iodide during fabrication. Such a process for introducing iodine into an iodide .additive lamp is discussed by Smith et al in the U.S. Pat. No. 3,279,877 issued on Oct. 18, 1966.

Thus, high-pressure mercury vapor lamps with strontium chloro-apatite phosphors are known in the art,

and high-pressure mercury vapor discharge lamps with titanium iodide additives are known in the art, but neiwith divalent europium is an efficient source for these 'purposes, but.is a relatively low-intensity source.

SUMMARY OF THE INVENTION It has been discovered that a high-pressure mercury discharge lamp having a titanium iodide additive and having a strontium chloro-apatite phosphor activated by divalent europium provides high-intensity blue light in a-very efficient manner. This high output of blue light is illustrated by the lamps blue-normalized output per watt value of about 200, and the 100 watts emitted in the 320-500 nm range by a 400 watt lamp.

The combination comprises a discharge lamp having an elongated light-transmitting arc tube enclosing the predetermined volume and containing apredetermined amount of mercury which, when fully vaporized during normal operation of the lamp will provide predeter- Y mined pressure of mercury vapor therein. The combiin treating infantile hyperbilirubeinemia. Although the nation also comprises an outer light transmitting envelope-spaced from and enclosing the arc tube. The improvement in the combination comprises a phosphor coating substantially comprising a strontium chloroapatite activated by divalent europium, which is coated on the interior surface of the outer envelope. The improvement also comprises discharge sustaining additives contained in the arctube, these additives substantially comprising titanium in the amount of at least about 0.005 milligrams (mg) per cubic centimeter (cc) of arc tube volume and iodine in an amount of about 0.002 to 0.2 mg per cc of arc tube volume. Titanium in excess of the amount which will react with the iodine BRIEF DESCRIPTION OF THE DRAWING For a better understanding of the invention, reference may be had to the exemplary embodiment shown in the accompanying drawing in-which:

The sole FIGURE is a side elevational view of a discharge lamp constructd in accordance with the present invention, with parts of the outer envelope and arc tube broken away.

DESCRIPTION OF-THE PREFERRED EMBODIMENT In the sole FIGURE there is shown the general arrangement of a high-pressure mercury vapor discharge lamp within which the discharge sustaining additives and the phosphor of the present invention are utilized. The lamp, generally designated 10, includes an outer light-transmitting envelope 12 which is sealed to a standard mogul base 14. Mounted within the outer envelope 12 and spaced therefrom is an arc tube 16. The are tube 16 is mounted within the outer envelope 12 by a conventional frame 18 and a pair of straps 20. Sealed within the arc tube 16 disposed at opposite. ends thereof are a pair of tungsten operating electrodes 22 and 24. The electrodes 22 and 24 are sealed through the opposite ends of the arc tube 16 by conventional ribbon seals 26. A starting electrode 28 is also sealed to the arc tube adjacent to electrode 24 by meansof a ribbonseal 26.

The frame 18 is carried by one of a pair of conventional lead-in conductors 30 which extends through a conventional re-entrant stern press 32 connected to mogul base 14, which in turn is connected to a conventional power source 34 in the well-known manner.

The electrodes 22, 24 and 28 are electrically connected to one or the other of the lead-in conductors 30. A starting resistor 36 is connected between one of the lead-in conductors 30 and the starting electrode 28 through the frame 18.

The discharge materials 38 are contained within the considerable variation. It will, however, normally require from about 1 to 8 mg of phosphor per square centimeter of coated area, and preferably require about 3 mg per square centimeter. While the phosphor coating can be a mixture with lesser amounts of other blueemitting phosphors with, for example. a bariumcalcium apatite activated by divalent europium an unarc tube 16. These discharge materials 38 contain titaon May 29*, l.956.

While the teachings of the present invention are applicable to discharge devices of varying size and designed wattage inputs, a specific example of a lamp mixed strontium chloro-apatiteis preferred.

The high-pressure mercury lamp with a titanium iodide additive and the high-pressure mercury vapor lamp with a divalent-europium activated strontium chloro-apatite phosphor coating, while providing reasonably high-intensity sources, are comparatively inefficient sources of blue light. When the titanium iodide additive is combined with the high-pressure mercurystrontium chloro-apatite lamp a lamp is produced which is, instead of having a blue output which is a compromise between these two types of high-pressure discharge lamps, has a blue output which is much greater than either one.

The lamp of the instant invention has a much higher intensity output than the strontium chloro-apatite fluorescent lamp. The 600 watt lamp of the instant invention has a blue-normalized ouptut of about 114,600

constructed in accordance with the present invention isillustrated as a standard 400 watts quartz arc tube 16 havingan l8 millimeter inside diameter and about 15 cubic centimeters of internal volume. Such a lamp when charged with a discharge sustaining filling of about 30-50 mg of mercury, 2 mg of titanium,and 2 mg of mercury iodide and operated at 400 watts (3.4 amps at about 127 volts) will produce, in conjunction with the strontium chloro-apatite phosphor activated by divalent europium, approximately 65 lumens per watt (as compared to 48 lumens per watt from a conventional europium activated strontium chloroapatite phosphor coated mercury vapor discharge lamp). When normalized I to the Z-bar spectral tristimulus curve (the desired output) the lamp of the instant invention gives an increase of about 100 percent of blue output over the conventional high-pressure mercury strontium chloro-apatite lamp (200 as compared to' 100 Similarly, the wattage emitted in the 320-500 nm range is doubled (100 watts as opposed to 50 watts for the high-pressure mercury-strontium chloroapatite).

while a 40 watt fluorescent has a blue-normalized output of only about 9,200. The lamp of the instant invention has the advantage of providing a relatively compact source which can be focused to provide an extremely high intensity, and even if multiple fluorescent lamps were used, they could not be focused in a practical manner. Thus, the instant invention provides the 'mostefficient high-intensity source of blue-normalized amount of mercury which when fully vaporized during of the present invention. The coating is applied in the conventional manner and the baking of such a coating is described in the aforementioned US. Pat. No. 2,748,303.

The amount of phosphor which is used is subject to normal operation of. said lamp will provide predetermined pressure of mercury vapor therein and an outer light-transmitting envelope having an interior surface spaced from and enclosing said are tube, the improvement which comprises:

' a. a phosphor coating substantially comprising strontium chloro-apatiteactivated by divalent europium on said interior surface ofsaid outer envelope; and

b. discharge sustaining additives contained in said are tube, said additives substantially comprising; i. titanium in the amount of at least about 0.005 mg per cc ofsaid arc tube volume; and ii. iodine in an amount of about 0.002 to 0.2 mg per cc of said arc tube volume, whereby said combination provides blue light in a very efficient manner. I

2. The combination of claim 1 wherein said titanium is present in the amount of about 0.13 mg per cc of said are tube volume, said mercury is present in the amount iodine is present in the amount of about 0.074 mg per cc of said arc tube volume. 

2. The combination of claim 1, wherein said titanium is present in the amount of about 0.13 mg per cc of said arc tube volume, said mercury is present in the amount of about 2.5 mg per cc of said arc tube volume, and said iodine is present in the amount of about 0.074 mg per cc of said arc tube volume. 